feat(queue): return promise from queue

Delegate to p-queue with concurrency=1

server/helpers/queue.js

@@ -1,7 +1,8 @@
+const {default: PQueue} = require("p-queue");
+
 /**
  * Return a queued version of the function `f`.
  */
-// TODO: Return a promise
 const queued = f => (q => () => q(f))(queue());
 
 /**
@@ -17,26 +18,9 @@ const queued = f => (q => () => q(f))(queue());
  * Registered workers are automatically evaluated in sequence.
  */
 const queue = () => {
-	let workers = [];
-	let running = false;
-
-	const run = async () => {
-		if (running) return;
-		running = true;
-
-		try {
-			while (workers.length) {
-				await workers.shift()();
-			}
-		}
-		finally { running = false; }
-	};
+	const pqueue = new PQueue({concurrency: 1});
 
-	// TODO: Return a promise, to make it async and enable promise error handling
-	return f => {
-		workers.push(f);
-		setTimeout(run, 0);
-	};
+	return f => pqueue.add(() => f());
 };
 
 module.exports = { queued, queue };

server/package-lock.json

@@ -359,6 +359,11 @@
       "integrity": "sha1-Cr9PHKpbyx96nYrMbepPqqBLrJs=",
       "dev": true
     },
+    "eventemitter3": {
+      "version": "4.0.0",
+      "resolved": "https://registry.npmjs.org/eventemitter3/-/eventemitter3-4.0.0.tgz",
+      "integrity": "sha512-qerSRB0p+UDEssxTtm6EDKcE7W4OaoisfIMl4CngyEhjpYglocpNg6UEqCvemdGhosAsg4sO2dXJOdyBifPGCg=="
+    },
     "external-editor": {
       "version": "3.0.3",
       "resolved": "https://registry.npmjs.org/external-editor/-/external-editor-3.0.3.tgz",
@@ -755,6 +760,28 @@
       "integrity": "sha1-u+Z0BseaqFxc/sdm/lc0VV36EnQ=",
       "dev": true
     },
+    "p-finally": {
+      "version": "1.0.0",
+      "resolved": "https://registry.npmjs.org/p-finally/-/p-finally-1.0.0.tgz",
+      "integrity": "sha1-P7z7FbiZpEEjs0ttzBi3JDNqLK4="
+    },
+    "p-queue": {
+      "version": "6.2.0",
+      "resolved": "https://registry.npmjs.org/p-queue/-/p-queue-6.2.0.tgz",
+      "integrity": "sha512-B2LXNONcyn/G6uz2UBFsGjmSa0e/br3jznlzhEyCXg56c7VhEpiT2pZxGOfv32Q3FSyugAdys9KGpsv3kV+Sbg==",
+      "requires": {
+        "eventemitter3": "^4.0.0",
+        "p-timeout": "^3.1.0"
+      }
+    },
+    "p-timeout": {
+      "version": "3.2.0",
+      "resolved": "https://registry.npmjs.org/p-timeout/-/p-timeout-3.2.0.tgz",
+      "integrity": "sha512-rhIwUycgwwKcP9yTOOFK/AKsAopjjCakVqLHePO3CC6Mir1Z99xT+R63jZxAT5lFZLa2inS5h+ZS2GvR99/FBg==",
+      "requires": {
+        "p-finally": "^1.0.0"
+      }
+    },
     "parent-module": {
       "version": "1.0.1",
       "resolved": "https://registry.npmjs.org/parent-module/-/parent-module-1.0.1.tgz",

server/package.json

@@ -28,6 +28,7 @@
 	"dependencies": {
 		"chrome-remote-interface": "^0.27.2",
 		"node-fetch": "^2.2.0",
+		"p-queue": "^6.2.0",
 		"semver": "^5.5.0",
 		"source-map": "^0.7.3"
 	},

server/spec/helpers/queue-spec.js

@@ -10,12 +10,12 @@ describe("Running queues", () => {
 		let result = [];
 		let workers = expected.map(n => () => result.push(n));
 
-		workers.forEach(q);
+		let promises = workers.map(q);
 
-		setTimeout(() => {
+                Promise.all(promises).then(() => {
 			expect(result).toEqual(expected);
 			done();
-		}, 100);
+		});
 	});
 
 	it("should run async workers in sequence", (done) => {
@@ -25,15 +25,16 @@ describe("Running queues", () => {
 
 		let result = [];
 
-		expected.forEach((n) => q(async () => {
-			await timeout(20);
+		let promises = expected.map((n) => q(async () => {
+                        // make the first ones slower than the later ones
+			await timeout((3-n)*20);
 			result.push(n);
 		}));
 
-		setTimeout(() => {
+		Promise.all(promises).then(() => {
 			expect(result).toEqual(expected);
 			done();
-		}, 200);
+		});
 	});
 
 	it("should run again when adding new workers", (done) => {
@@ -46,24 +47,23 @@ describe("Running queues", () => {
 			result.push(n);
 		});
 
-		workers.forEach(q);
+		let promises = workers.map(q);
 
-		setTimeout(() => {
+                Promise.all(promises).then(() => {
 			expect(result).toEqual([ 1, 2, 3 ]);
-			done();
-		}, 100);
+		});
 
 		let newWorkers = [ 4, 5, 6 ].map(n => async () => {
 			await timeout(20);
 			result.push(n);
 		});
 
-		setTimeout(() => newWorkers.forEach(q), 300);
+		promises = newWorkers.map(q);
 
-		setTimeout(() => {
+                Promise.all(promises).then(() => {
 			expect(result).toEqual([ 1, 2, 3, 4, 5, 6 ]);
 			done();
-		}, 400);
+		});
 	});
 
 	it("queues should not evaluate other queues workers", (done) => {
@@ -76,19 +76,19 @@ describe("Running queues", () => {
 		let result1 = [];
 		let result2 = [];
 
-		expected1.forEach(n => q1(() => result1.push(n)));
-		expected2.forEach(n => q2(() => result2.push(n)));
+		let promises1 = expected1.map(n => q1(() => result1.push(n)));
+		let promises2 = expected2.map(n => q2(() => result2.push(n)));
 
-		setTimeout(() => {
+		Promise.all([...promises1, ...promises2]).then(() => {
 			expect(result1).toEqual(expected1);
 			expect(result2).toEqual(expected2);
 			done();
-		}, 100);
+		});
 	});
 });
 
 describe("queued functions", () => {
-	it("can queue functions", (done) => {
+	it("can queue functions", async (done) => {
 		let count = 0;
 
 		let increase = () => {
@@ -97,13 +97,11 @@ describe("queued functions", () => {
 
 		let queuedIncrease = queued(increase);
 
-		queuedIncrease();
-		queuedIncrease();
-		queuedIncrease();
+		await queuedIncrease();
+		await queuedIncrease();
+		await queuedIncrease();
 
-		setTimeout(() => {
-			expect(count).toBe(3);
-			done();
-		}, 10);
+		expect(count).toBe(3);
+		done();
 	});
 })